With advances in technology, semiconductor light emitting devices are being used in a variety of applications, including home lighting, area lighting, vehicular lighting, and so on. Within these applications, particular luminance patterns may be desired to optimize the efficiency or effectiveness of the provided illumination.
The illumination (luminous intensity, luminance pattern) of a conventional light emitting device is generally Lambertian with respect to a normal to the emission surface. In the creation of a light emitting structure that provides a desired illumination that is not Lambertian, an optical element is used to convert the Lambertian luminance pattern into the desired luminance pattern.
For example, a “flashlight” application may employ a Fresnel lens that collimates the Lambertian luminance into a luminance pattern having a narrow beamwidth, thereby concentrating the light in a direction orthogonal to the lens.
In automotive applications, such as a headlight, an elongated luminance pattern may be desirable such that the luminance pattern has a somewhat broad beamwidth in one dimension (across the roadway) and a narrow beamwidth in the other dimension (above the roadway). FIG. 1A illustrates a cross-section profile of a “peanut-shape” optical lens 14 as disclosed in U.S. Pat. No. 7,339,200, “LIGHT-EMITTING DIODE AND VEHICULAR LAMP” issued to Amano et al., 4 Mar. 2008, and incorporated by reference herein. In the longitudinal direction, the lens comprises two convex lens section C2 on either side of a concave lens section C1. This combination of lens sections serves to disperse the light emitted by the LED 110, and provides the luminance pattern 150 of FIG. 1B with two peaks at a given angle off from the normal of the light emitting surface. The various dimensions of the optical lens 14 with respect to the location of the LED 110 determine the location (angle off normal) and magnitude of these peaks, as well as the magnitude of the luminance in the ‘valley’, normal to the light emitting surface.
Although the costs of molding or otherwise forming an optical lens that creates a desired luminance pattern may be slight, increasing competitive pressures in the field of semiconductor light emitting devices often require cost reductions wherever feasible.
Additionally, for cost effectiveness and other considerations, the forming of the desired optical lens is generally performed during the ‘packaging’ phase of manufacturing the light emitting structure, thereby requiring that the manufacturer of the light emitting structure be involved in creating a lens that provides the desired luminance pattern.